Fuel gas conditioning

Abstract

Compressed rich natural gas is divided into a cooling gas stream and a fuel gas stream. The cooling gas stream is depressurized. The cooling gas and the fuel gas are then heat exchanged to provide a first cooling step to the fuel gas. The cooled fuel gas continues into a second cooling step in a second heat exchanger, and then flows into a separator vessel where liquids are removed from the bottom of the separator and conditioned fuel gas exits the top of the separator. The conditioned fuel gas from the separator and produced from its influent is depressurized and heat exchanged to provide the second cooling fluid for the second heat exchanger.

I claim: 
     
       1. A method to condition fuel gas, the method comprising:
 depressurizing a first fraction of a feed stream with a first depressurization valve ( 6 ); 
 
       passing the first fraction of the feed stream through a cold side of a first heat exchanger ( 11 ); 
       passing a second fraction of the feed stream through a hot side of the first heat exchanger; and
 splitting an effluent from the hot side of the first heat exchanger into a lean fuel gas stream ( 17 ) and a natural gas liquid (NGL) stream ( 20 ) with a scrubber ( 19 ) wherein the scrubber is positioned downstream from the hot side of the first heat exchanger. 
 
     
     
       2. The method of  claim 1 , further comprising:
 cooling a hot side effluent from the first heat exchanger with the lean fuel gas stream using a second heat exchanger ( 16 ) downstream from the first heat exchanger before the scrubber creates the lean fuel gas stream and the NGL stream. 
 
     
     
       3. The method of  claim 2 , further comprising:
 depressurizing the lean fuel gas stream from the scrubber with a second depressurization valve ( 14 ) upstream of a cold side of the second heat exchanger. 
 
     
     
       4. The method of  claim 3 , wherein the second depressurization valve:
 cools its effluent stream to a temperature below approximately −20° F.; and 
 reduces a pressure of its effluent stream to about below 100 PSI. 
 
     
     
       5. The method of  claim 1 , wherein the lean fuel gas stream exits the system below 100 PSI and below 80° F.